Open Access

Geydar Agakishiev, Oliver Werner Arnold, Daniel Belver, A. Belyaev, Jia-Chii Berger-Chen, Alberto Blanco, Michael Böhmer, Jean-Louis Boyard, Pablo Cabanelas Eiras, Sergey P. Chernenko, Adrian Dybczak, Eliane Epple, Laura Fabbietti, Oleg Fateev, Paolo Finocchiaro, Paulo Fonte, Jürgen Friese, Ingo Fröhlich, Tetyana Galatyuk, Juan A. Garzón, Roman Gernhäuser, Kathrin Göbel, Marina Golubeva, Diégo González-Díaz, Fedor Guber, Malgorzata Gumberidze, T. Heinz, Thierry Hennino, Romain Holzmann, Alexander P. Ierusalimov, Ileana Iori, Alexander Ivashkin, Martin Jurkovič, Burkhard Kämpfer, Tatiana L. Karavicheva, Ilse Koenig, W. Koenig, Burkhard W. Kolb, Georgy Kornakov, Roland Kotte, Antonin Krása, Filip Krizek, Reiner Krücken, Hubert Kuc, Wolfgang Kühn, Andrej Kugler, Tobias Kunz, Alexander Kurepin, Vladimir P. Ladygin, Rafał Tomasz Lalik, Kirill Lapidus, Alexei Lebedev, Luis Alberto Vieira Lopes, Manuel Lorenz, Ludwig W. Maier, Alessio Mangiarotti, Jochen Markert, Volker Metag, Jan Michel, Christian Müntz, Robert Helmut Münzer, Lothar Naumann, Yvonne C. Pachmayer, Marek Palka, Yannis Parpottas, Vladimir Pechenov, Olga Pechenova, Jerzy Pietraszko, Witold Przygoda, Béatrice Ramstein, Andrey Reshetin, Anar Rustamov, Alexander Sadovsky, Piotr Salabura, Alexander Schmah, Erwin Schwab, Johannes Stephan Siebenson, Yuri G. Sobolev, Stefano Spataro, Björn Spruck, Herbert Ströbele, Joachim Stroth, C. Sturm, Attilio Tarantola Peloni, Khaled Teilab, Pavel Tlustý, Michael Traxler, Haralabos Tsertos, Taras A. Vasiliev, Vladimir Wagner, Michael Weber, Christian Wendisch, Jörn Wüstenfeld, Sergey Yurevich, Yuri V. Zanevsky, Andrei V. Sarantsev

• Employing the Bonn–Gatchina partial wave analysis framework (PWA), we have analyzed HADES data of the reaction p(3.5 GeV) + p → pK +Λ. This reaction might contain information about the kaonic cluster “ppK −” (with quantum numbers J P = 0− and total isospin I = 1/2) via its decay into pΛ. Due to interference effects in our coherent description of the data, a hypothetical KNN (or, specifically “ppK −”) cluster signal need not necessarily show up as a pronounced feature (e.g. a peak) in an invariant mass spectrum like pΛ. Our PWA analysis includes a variety of resonant and non-resonant intermediate states and delivers a good description of our data (various angular distributions and two-hadron invariant mass spectra) without a contribution of a KNN cluster. At a confidence level of CLs = 95% such a cluster cannot contribute more than 2–12% to the total cross section with a pK +Λ final state, which translates into a production cross-section between 0.7 μb and 4.2 μb, respectively. The range of the upper limit depends on the assumed cluster mass, width and production process.